The present invention relates to a method using high interior pressure to reshape structural section.
The structural section being reshaped using high internal pressure may be tubing as disclosed in German 3 923 358 A1 and in U.S. Pat. No. 4,414,834 A. Pieces with a non-circular cross-section, however, can also be reshaped. Such material is usually extruded.
To ensure unobjectionable fluid tightness, a stopper is forced radially against each end of the structural section. The end of the piece rests against an edge of the stopper, creating a seal. To reduce wear on the stoppers as much as possible, the seal-creating edge is made of a wear resistant material and is forced against the interior surface of the section subject to relatively high pressure.
It would also be desirable to similarly use high interior pressure to reshape pieces with extra walls or chambers projecting into or out of their overall cross-section. There is, however, a drawback to such a procedure in that the walls or chambers tend to deform axially along the piece, allowing the edges to buckle or bulge out axially undefined. It is of course possible to counteract this tendency by making the edges of a softer material. This approach, however, increases wear on the edges.